Nowadays, many mobile terminals have a Secure Digital (SD) interface, so that the mobile terminals can support an SD card. Because the SD card has features of a small size, large capacity, and plug-and-play, the SD card is generally used as an external storage device of a mobile terminal for storing data. Furthermore, the mobile terminal may use the SD card to update firmware.
The process of using the SD card to update firmware by the mobile terminal may be as follows. After a firmware update file is copied to the SD card, the SD card is inserted into an SD interface, so that the SD card is connected to the mobile terminal. The mobile terminal reads the firmware update file in the SD card to update software of the mobile terminal.
The mobile terminal may further insert a communication device having an SD interface into the SD interface. The communication device having the SD interface may support access to a Second Generation (2G), Third Generation (3G), or wireless network. Therefore, the mobile terminal can perform wireless Internet access through the communication device having the SD interface.
When the SD interface supports a Secure Digital Input and Output (SDIO) function, the communication device having the SD interface can write a firmware update file in the mobile terminal to an SD memory of the mobile terminal. After reading an update start command in the mobile terminal, the communication device having the SD interface runs the firmware update file in the SD memory to complete a firmware update.
However, some SD interfaces do not support the SDIO function. A communication device having such an SD interface cannot know, through the SD interface, whether data read by the communication device from the mobile terminal is an update start command, and further, the communication device having the SD interface cannot start a firmware update.